Apparatus for lamp bulb sealing



R. B. THOMAS APPARATUS FOR LAMP BULB SEALING Filed March 6, 1959 2 Sheets-Sheet l FIALPH 5, 771mm;

FUWEE SO (/ECE INVENTOR ATTORNEY.

Dec. 9, 1947. THOMAS 2,432,491

APPARATUS FOR LAMP BULB SEALING 4 Filed March 6, 1959 2 Shets-Sheet 2 RM PH 5. TH om 6,

nynsxmR. BY a Patented Dec. 9, 1947 UNITED SATES PATENT FHCE APPARATUS FOR LAMP BULB SEALING Ralph B. Thomas, Beverly, Mass., assignor to Hygrade Sylvania Corporation, Salem, Mass, a corporation of Massachusetts Application March 6, 1939, Serial No. 260,103

1 Claim.

This invention relates to electric lamps, and in particular to the sealing together of the glass parts of such lamps.

An object of the invention is the provision of an accurately aligned seal between the bulb and stem of such a lamp. Another object is to insure that the interior the lamp will not b contaminated by any foreign gas or vapor, such as would be present if the seal were made by the usual gas flame.

A further object is to provide a simple electrical apparatus for sealing the stem and bulb of a lamp together.

Other objects and advantages of the invention will be apparent from the following specification, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a profile view, partly in section, of sealing apparatus according to the invention;

Figure 2 is a perspective View of a carbon ring according to the invention;

Figure 3 is a plan view of the top bulb holder of Figure 1;

Figure 4 is a plan view of the lower bulb holder of Figure 1;

Figure 5 is a plan view of the stem holder.

Figure 1 shows apparatus for effecting the seal. The lamp bulb I, is guided near its top by the transverse support l2, attached to the vertical metal rods l3 and I4, and is held near its other end by the clamp l5, which keeps it in proper alignment. The lamp stem 2, rests on the carbon ring l8, which rests on the flange 53 of the stem holder 28 of refractory insulating material, which in turn rests on the refractory piece l6, of insulating material, fixed to the metal piece 39, by the refractory insulating rods 4|. The end of the rods 4| may be fixed to the ends of the pieces 39 and 16 in any convenient manner, as by cementing. The refractory tube I! which is an integral part of the stem holder 28, serves to protect the exhaust tube 1, and is capable of sliding in the hole 42 in refractory piece IS. The closed carbon ring I8, is placed on the flange 53 of the stem holder which serves to hold the ring in contact with the flare of the stem. The lamp bulb I, is arranged so that its neck is in contact with the flare of the stem 2.

Below the stem holder is the coil i9, which may be connected to a high frequency power source 52, and which is preferably surrounded by the insulating refractory tube 20, for the safety of the operator and also to prevent air currents through the coil to protect the seal.

The coil may be of edgewise wound copper ribbon, supported, for example, by being screwed at i Z the bottom end 43, to the insulating refractory piece 38, and at its top end 4 1, by being screwed to the refractory tube at, surrounding the coil. The top and bottom ends may be connected to a source of high frequency energy, such as a vacuum tube oscillator of sufficient power.

The bulb holder and stem holder support 16, are held in proper relation by being supported from the rods I3 and M, the piece St, and the insulation refractory rods 4|. The rods, I3 and M, in turn are supported fro-m the back rods 2| and 22, by the rectangular frame 39 which is arranged to be capable of sliding along the rods 2i and 22. While the bulb and stem are being placed in their respective holders, the latch 23 engages the stop 24, holding the assembly up. When the assembly is dropped to place the coil around the carbon ring, so that they will be in proper inductive relation, the stops 25 and 2B limit the downward journey at the proper point.

In operation the stem is placed on the stem holder 28, above the carbon ring 58, the lead wires and exhaust tube, if present on the stem, going into the tube IT. The stem holder will be supported by the refractory piece it. The top of the bulb is inserted in the opening Aid in the top bulb holder [2, and the lower part of the bulb is pushed back into the lower bulb holder 15, the jaws of the lower bulb holder being separated for the purpose by means of the handle 38, as shown in Figure 4. These holders keep the bulb in line, the spring 31 being strong enough to cause the jaws 3| and 32 to hold the bulb firml against the pull of its own weight and the eventual push, to be explained later, of the spring 49, The latch 23 is released, allowing the supporting assembly to drop to the stop 25.

The coil I9 is then energized by passing through it a current of high frequency, say one million cycles per second. This heats the carbon ring is by induction, the ring acting as a closed turn of a transformer. The ring may be heated to about 1100 C., or to a temperature sufficient to fuse together the glass of the stem 2 and bulb l at their junction. To prevent cracking the glass by a too rapid rise in temperature, it may be desirable to heat the carbon for a short period, shut off the power for a short period, and then heat the carbon for a longer period. The same effect may be achieved by energizing the coil before the carbon ring is lowered into it, and then lowering the ring and the glass into the coil slowly enough to avoid too rapid heating of the glass.

On lowering the frame 39 to plac the carbon ring inside the coil IS, the lower end of the refractory tube ll will meet the top 50 of the rod 46 of insulating material, which piece is capable of sliding in the piece 45 affixed to the base 5|. The piece 46, will be pushed down against the spring 49 until the downward movement of the assembly frame 39 is limited by the stops 25 and 26, which stops may be arranged so that the rod 46 is pushed down about one-sixteenth inch. When the glass is heated sufficiently to become softened the spring 49 will then push the rod 46 and the tube I? up about one-sixteenth inch, so that the stem holder 28, of which the tube 11 is an integral part, will rise the same distance above refractory piece 16, pushing the lamp stem 2 firmly against the end of the glass tube 1 and insuring that the glass parts are properly merged together to form a perfect seal. The spring 31, shown in Figure 4, of the tube clamp I5 should be strong enough to hold the jaws 3| and 32 firmly enough against the glass tube to prevent the tube from moving when the softened stem is pressed against it.

This piece should extend far enough from the coil E9 to keep the metal spring from being overheated by induction from the coil. The annular metal ring ll is placed at the bottom of piece 45, to which it is secured by screws or the like, and may serve to hold the spring 49. A similar ietal ring 49 may be attached to the rod 46. The metal rings act as stops to limit the distance the spring can push the stel 2, when the latter softens, although other forms of stops can, of course, be used.

It will be seen that the timing of the movement exerted against the seal is automatically fixed by the seal itself. As soon as the glass melts, the spring 49 moves the top 59 against the tube 5! which moves the carbon ring to compress the glass the desired distance. After the glass has softened and the stem and bulb are properly joined, it is desirable to raise the frame 39 enough so that the holder 28 may drop back against the refractory piece 56, enabling the carbon ring and the stern also to drop back under gravity, thus pulling out the seal slightly to improve the seal.

After the seal is eiiected, the carbon may be allowed to cool for a short period, a minute for example, and the assembly may be raised to the position where it is supported by the latch, the lamp separated from the carbon, and the carbon used again.

If the carbon ring H}, be separated from the-seal immediately after the seal is formed, it will pull some of the glass with it, spoiling the seal. Shortly after the glass has begun to harden, the ring will be firmly attached to the glass, and cannot be removed without cracking the seal. After a little more cooling, in many cases a minute after the seal is completed, the ring can be gently pulled away from the glass with no ill efiects on the seal. If the glass is cooled still further, the ring will separate from the glass by its own weight, but that stage of cooling generally requires too long a period for use in efiicient automatic machinery, the stage where the ring can be pulled away from the seal without harm being generally better for such machinery. If the carbon ring has a somewhat roughened surface, the seal also will have a roughened surface, and will give better contact with the cement used for affixing a contact base.

Figure 4 shows a plan view of the lower bulb holder H5. The two jaws, 3i and 32, are-made to move in opposite directions by the gears, 33 and 34, the jaws being pivoted on the pins, 35 and 36, and normally held together by the spring 31. Jaw 32 has the handle 38 to open the jaws for inserting the bulb. The spring 31 is strong enough to bring the jaws together, to keep the bulb from slipping downward of its own weight, and to hold it against the push of spring 49.

Figure 3 shows the top bulb holder l2, in plan view, the hole for the lamp bulb or tube being marked 40. The piece l2 may be of refractory material, such as a solid asbestos material.

Figure 2 shows a carbon ring l8, such as is used with the invention, in perspective.

In Figure 5, the refractory piece [6, which serves as a stem holder support, is shown in plan. view. The refractory tube ll which serves to protect the exhaust tube 7 of the stem 2, and which also aids in centering the stem on the holder, slides freely through the hole 42 in the center of the piece 16. Refractory insulating support rods 4| extend from the circumference of the piece upward to be attached to the piece 39, as shown in Figure 1.

For simplicity, in Figure 1, the filament or electrode and the lead-in wires supporting it are not shown in the stem 2.

What I claim is:

In a glass bulb sealing machine, a refractory piece of insulating material, a stem holder of refractory insulating material comprising a tube passing through said piece and having an extending shoulder and flange on one end, an annular carbon ring on said holder, rods of refractory insulating material projecting upward from said refractory piece, a metal plate from which said rods are supported, spring jaws mounted on said metal plate in position to hold securely a tubular glass bulb in register with the axis of the carbon ring, a coil of electrically conductive material in register with the aXis of the carbon ring and of a diameter large enough to allow the insertion into the coil of the carbon ring and its associated apparatus below the metal plate, a source of high frequency voltage connected to the ends of said coil, means for inserting said carbon ring and said associated apparatus in said coil to heat said ring and melt the glass of the stem flare and abutting end of the tubular bulb, and means for pushing the carbon ring a limited distance into the melted glass.

RALPH B. THOMAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,572,873 Allcutt Feb. 16, 1926 1,904,214 Fagan Apr. 18, 1933 2,048,556 McArthur July 21, 1936 2,121,627 Donovan et al June 21, 1938 2,125,316 Ronci Aug. 2, 1938 2,203,917 Malloy June 4, 1940 2,272,927 Stager Feb. 10, 1942 FOREIGN PATENTS Number Country Date 474,947 -Germany Apr. 15, 1929 542,173 Germany Jan. 22, 1932 

